Soaking, freezing, and drying by sublimation of untanned hides



' March 2.3, 1948.

w. M. CUTLER AND DRYING BY SUBLIMATION 0F UNTANNEDl HIDES SOAKING, P REEzING,

Fuer: April 22, 1944 this Q Sw U .fm/en tof' Wallace M Cutler' Attorney term being to Patented Mar. 23, 1948 SOAKING, SUBLI Wallace M. Cutler,

United Shoe Machinery Corporation,

FREEZING, AND DRYING BY TION OF UNTANNED HIDES Gloucester, .Mass., assignor to Flemington, N. J., a corporation ofNew Jersey Application April 22, 1944, Serial No.

This invention relates to methods of treating A untanned hides and skins and to the products produced thereby. More lspecifically the invention relates to .methods oi treating hides and skins which involve the steps of soaking and freezing an untanned hide or skin freshly vremoved from the carcass of an animal and then drying it at subireezing temperatures to prepare it for subsequent operations, depending upon the nature of the product desired. Invention is also to be recognized as residing in both tanned hides or skins as well as in untanned hides or .skins prepared as articles of commerce in accordance with the new method. It is to beunderstood that the method, when carried out, is VnotV limited to use of any particular machines and/or apparatus.

This application is a continuation .in part of application Serial No. 367,055, filed November 2'5, 1940, which has matured into Patent No. 2,354,200 and is entitled Method of l'drying vhides and skins. In the present application, when hides alone are spoken of, both hides and skins are referred to, the purpose in using the `single eliminate verbiage.

It is an object of this invention `to treat nntanned hides in such a way that the .untanned product will be improved as to ease and expense in handling, will 'be less subject to bacterial action with its consequent loss of hide substance yand quality, and be more easily susceptible to subsequent tanning. Another object is to yprovidea method of hide treatment in which the necessity of shipping or storing of untanned hides in salt and by such elimination to -avoid shipping and storage charges on excess weight due to salt and water. A further object is to provide a method and product, both of which permit clean and pleasant working conditions for the personnel handling the hides. Still another object is to promptly stop putrefaction of ,fresh hides and, as a consequence, to avoid localized hide stains and general hide quality deterioration as well as actual loss in hide substance and area. Another object is to secure a light weight, high quality, untanned hide which can .be packed, stored or which, if it is desired, may be used for the manufacture :of leather .as soon as produced, the time of production being low. Still another object is to produce a preserved untanned hide which with a considerable saving in time may be subsequently tanned in a conventional manner or in the manner .taught in the said Patent No. 2,354,200, referred to above. Another object is to combine the present improved method for producing an untanned hide with any conventional tanning method or with the method disclosed in the said patent to secure an improved leather. Yet another object is the production of a tanned hide `of eXcellentvand improved quality with all its useful substance intact.

In the practice oi my invention, a fresh .untanned hide is rst given a wash to remove foreign matter adhering to it in the slaughter house. In case excess ilesh should remain on the hide, because of imperfections in the'carrying .out of the process of -flaying, the hide is scraped to Residual flesh will materially slow down the drying process if not removed. The hide is then soaked in water preferably containing some agent such as salt to aid in remov ing water-soluble proteins although that is not essential (such proteins do not form leather substance when a hide is subsequently tanned) and the soaked hide is then rinsed with water to cleanse the hide of such agent and/or other `foreign matter. The hide then contains an appreciable amount of water and while in that condition is frozen. As a result of the freezing operation, the hide substance is expanded, -due to the presence of ice crystals formed in the spaces or interstices between the iibers and brils of the hide substance. The rate of freezing is controlled in accordance with the characteristics of the product desired. Apparently the slower the freezing operation, the larger the ice crystals will be and hence the greater the expansion oi the interstices or spaces in the hide substance, with the result that the slowly frozen hide results usually in being the plumper and softer hide was compared with a h'de which is subjected to quick freezing. However that may be, the frozen hide is then dried by contacting it with a waterabsorbing medium, the hide being maintained under subireezing conditions with no or slight thawing being perm'tted. The drying should be largely by sublimation if the advantages of the present invention are to be achieved. Whereas a fresh or green hide or skin has a specific gravity of about 1.050 to about 1.075, the same hide dried by the method herein described has a much lower specific gravity and a calfskin correspondingly dried has a speciiic rgravity of about .344 as will be seen in a table of test results to be subsequently referred to. Green hides and skins l(containing, as is usual, more than onehalf their weight in water after the flaying operation) which have been dried in the open air are hard or horny and much shrunken with a specic gravity lof about .775 to about 1.40. Plump, light weight, soft and untanned hides produced by the present method may be conveniently packaged method will not usually be continued to the point r merely stacked and are preserved, because of where it may be said to be bone-dry, this for their dryness, against bacterial action until subthe reason that all hides and skins readily take 2,354,200 advantages such as a considerable savit contains moisture in the range of about 8% to ing in time and hide substance are secured in 13%, that is until 1t reaches what may be termed the carrying out of that process by using the unan air-dry condition. A greater amount of tanned hides produced with the new method l moisture may be left in the hide but that amount herein disclosed. should in no case be suieient to promote bac- These and other important advantages and teria] growth or action.

characteristics of the method and of the products As indicated above, a marked advantage of will now be described in detail in the specication c the present method of treating untanned hides and then pointed out more particularly in the 15 resides in the fact that such hides arev preserved appended claims, by the treatment, it being possible to store them Y In the drawing, the single figure is a diagram-'- andship them Under Ordinary atmOSpheric 00nmatie flow sheet representing by way of. exampleY ditions of temperature and humidity, care beine ,the steps of the newrinethod and the order'in taken (of course) to see that no Water touches which they may be followed. Y Y i them. Hides placed ina dryor an air-d ryf con- Following the iiow diagram the hide V(promptly dition will be preserved for an extensive period after removalr from the animal carcass)- is iii-st as the presence of at least 20% moisture is or'- side is then "iieshed or scraped lto remove any ticed methods, hides and skins'must be treated until Yits weight has appreciably increased and shipment to the tanners "and that such'hides following that step, the hide is washed or rinsed and skins must be handled in bundles or in'casks to remove foreign matter. The water bath 'may for which a special freight Cal must be emblifed, have in it some agent such'as commensali; or 30 because of the malodorous condition that' prevails sodium polysulphide to aid in removing waterin spite of the most careful preservative treatsoluble proteins from the untapped hides a1- ment, it will be understood that very considerable though use of such an agent is not essential expense has heretofore been involved in preservagent toasubstantial degree before the process 'ab tanneis- FurthelmOIe, the banner `has had to the hide during thestepsA through, F on the tion consumes Vfrom Vone to five days Ottime,

medium, Such as air, is brought in Contact with of the care exercised by those responsible for the condition; by sublimation'ef its water content. stance due to putrefa'ctive changes'andto hy`` In order to insure that the moisture is removed drolysis of hide substance in the soaking operafrom the hide by a process of sublimation, the ti011- Y temperature of the hide is conveniently kept at It iS a marked advantage of the drying method about 26 F. However, this temperature may be and theV product disclosed herein that hides and 30 F'. and about 20 E. It is clear that drying 30 putrefactive changes but because of their'cleanliperformed at a temperature relatively high in neSS and light Weight they may be handled at the given range is more economical than at a a minimum of expense and, if desired, they may lower temperature. This drying by sublimation be conveniently packaged o r stacked to facilitate may becarriedout with the-,temperature of the the handling. A

owing, air or other drying medium being main- Another marked and important advantage of Vthe t tained even above that of the hide. The essential factor Yis that the drying is by sublimation out steps A to F (see the ow sheet)` in order to and not by evaporation. It will be readily unproduce a hide ready for the tannery need not derstood that'the rate at which hides or skins exceed 36 hours. Contrast this short period with are dried may be regulated'by the, amount, and 70 the minimum period of 30 to 60 days which is drying chamber, by the rapidity of its circulais packedin salt in the conventional manner used tion, and by the amount of the air dehumidifying in this country. agent if such an agent is used. It will be un- The plump, untanned, freezedried hide or skin derstood also that the drying of a hide by this has another advantage and that is appreciated e hod isV that the time involved in carrying when th'e hide or `skin is to be wet back, which constitutes a preliminary essential step at the tannery. As it Ais plump :and open in structure, it wets back quickly. It takesfour or five .days for an ordinary dry hide to wet back sufficiently for tanning. Inthe case'of wet salted calfslns it takes from .l to 12 hours. With Wet salted hides 'it takes 20 .to 25 hours. The following table of test-results shows that the rst seven samples (which were produced by using applicants process) are capable of 'rapid wetting back and are superior, in this respect, to wet salted hides. The last four columns of the said table of test-results serve to illustrate that the soaked and Ifreeze-dried. samples l. to 'l were far superior to the horny samples 8 to 16 (not properly freeze-dried) in their ability to 'assimilate water:

for 'eachmethod- "In each-method ofl tanning, however,.it islessentiall that the untanned hide iirst be wet back or soaked land it is in this connection .that the plump, freeze-.dried and untanned `hide facilitates the operations carried on in a tannery. In so far as the vegetable tanning is concerned, the drawing shows, vby-wayof examples, the. Asteps which may be taken' in the treatment `of hides to produce heavy or sole leather. Excellent chrome-tanned leather has been produced from a plump, freeze-dried calfskln by using a, conventional method similar to that shown at the far left of the flow diagram. In the event that .the `method of tanning disclosed in the Patent No. V2,354,200 is used, soaking time is also saved and the entire process from the fresh hide to finished leather will involve two separate stages of drying by sublimation to yield excellent MMM-MMM Per cent lick-up 4in Weight o( Shaved Sam- D it f Ifile: mixing 13% H2O Y ens .v o e ore 1c -up sodnsfnagnd giga Drying D ne Shaved Sam- Appearance and Time, Hrs' Watte)r Treatment lngg pile 55.13% Feel of Product Hours in Water at 0.3 Firm W hito Plump. 72. 0 211 215 225 0.3 ...do 150.0 228 228 216 0.33 do 57.0 202 212 216 U. 255 d0 178.0 248 270 228 0.427 do 37.0 148 167 177 0. 45 Firm Gray Plump. 34. 0 170 208 190 0. 345 Firm White Plump. 123. 0 212 212 236 0. 805 Horny 7. 0 63 77 125 0.89 .d0 6.3 63 81 125 0.85 do 5. 7 80 98 145 0.825 do 6. 2 74 103 153 .do. 0.90 do 4.9 49 75 124 Freeze Dried 0.92 do 4. 0 L17 6l 114: Air Dried 0.72 do. 6.2 66 79 112 Freeze Dried 7... 0.88 do- 4. l 44 7l 118 -d 0.92 do- 3. 6 62 91 116 In analyzing the above table, it can be seen that samples 1 to 7 inclusive illustrate the fact that soaking and freeze-drying produce excellent results. It should be noted that samples 1 to '7 inclusive, when dried by applicants method, had a density substantially below 0.72-that is, substantially below the lightest product made from samples 8 to 16 inclusive. Samples 8 and 13 show that freeze-drying without soaking is of no avail (other than, of course, that it inhibits bacterial action during the time the hide is frozen). Samples 9 to 12 inclusive and 14 illustrate that merely air-drying a hide will result in a horny product difficult to wet back for tanning purposes. Samples and 16 show that results are not satisfactory if care is not taken that the hides are actually freeze-dried or dried by sublimation. In the latter samples, the agent (salt) was apparently not adequately washed out, with the result that the ice in the samples melted during the drying step. When this occurs, the open spacial structure of the hide is not maintained, yielding a horny product which will not readily receive moisturei. e.-wet back rapidly.

When the plump untanned product has reached 'a tannery it may be treated in a number of ways, as shown by the flow sheet. It may be tanned by either the chrome or the vegetable tanning meththese methods may be conventional or they may be as taught in the above-referredto earlier Patent No. 2,354,200 and shown as the Cutler method in the flow sheet. It is to be understood that infinite variations in all these methods can be used and that only one of the many possible orders ci steps are shown in the diagram eliminate leather which has not been weakened at any by bacterial action, excessive shrinkage or violent treatment. In this latter method, the hide to be chrome tanned is maintained in a damp or wet condition during the conventional pretanning and tanning steps and also during fat liquoring and coloring before it is again frozen and dried. 1f the hide is to be vegetable tanned, then it is kept wet during the unhairing, hating and tanning steps and then frozen and dried by sublimation to secure an excellent product.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of treating a fresh untanned hide which comprises soaking the hide in water to apprecie-bly increase its weight, freezing the hide, and contacting the frozen hide with a water-abscr while said hide is maintained under subfreezing conditions to dry the hide b-y sublimation.

2. A method of treating a fresh untanned hide which comprises soaking the hide in water to appreciably increase its weight, freezing the hide at a controlled rate dependent upon the characteristics of the product desired, and contacting the frozen hide with flowing air while said hide is maintained under subfreezing conditions to remove water from the hide by sublimation.

3. A method of treating a fresh untanned hide which comprises soaking the hide in water containing an agent to aid in removing water-soluble proteins, washing the hide with water to largely the agent, freezing the hide, and conto produce leather which comprises soaking the 5 hide in water to appreciably increase its weight, freezing the hide, contacting the frozen hide with a water-absorbing medium under subfreezing temperature conditions to bring the hide to a condition suiciently dry to inhibit bacterial ac- 10 tion, and subsequently subjecting the dried hide td a tanning procedure.. Y'

' 5.. An untanned substantially air-dry hide having a density substantially below 0.72, said hide being prepared in accordance with the method of 15 claim 1.

' M. CUTLER.

.8V l REFERENCES CITED The following references are of record inA the file of this patent:

UNITED STATES PATENTS Nuinber Name Y Date Y 2,102,699 Green Dec.. 21; 1937 2,354,200 Cutler July 25, 1944 FOREIGN PATENTS Number Country Date` 12,642 Great Britain 1905 

